The present irrigation apparatus is designed to automate sprinkling of a field by use of a wheel-supported lateral pipeline having a plurality of sprinklers spaced along a center pipeline axis. A lateral pipeline is selectively supplied with water from a stationary water supply line having a plurality of water discharge valves spaced along its length. The apparatus is alternately in a stationary mode adapted to be hydraulically coupled to the water supply line through a selected water discharge valve, or in a traveling mode uncoupled from the water supply line and with the lateral pipeline powered for movement in a direction parallel to the supply line. The novel combination comprises a carriage guided along the water supply line, a structural fluid connection between the lateral pipeline and the carriage and sensing means for indexing the carriage by reference to a selected water discharge valve. A valve actuator on the carriage completes a hydraulic circuit from the water supply line to the lateral pipeline through the structural fluid connection. The entire apparatus is controlled sequentially from the carriage.